We use 19" TV's, one in the camper and one in our screen room that has flaps to close it in like a tent. The issue is that the TV speakers are on the back, so I have to turn it up kind of loud to hear it ( my hearing is not so good). That creates the situation that it's louder outside the screen room than inside, so a pair of remote speakers does help as I can point them at me. However the ones I have do require to be plugged in to 110V. Sometimes I use a set of headphones. I like the wired ones, tried wireless but didn't like them

If you have a built in radio in the trailer with speakers and your TV has a headphone jack you can use a Digital FM Transmitter - it will sent the sound from the TV to the trailers built in stereo system and play through the speakers you already have in the trailer.

I have a JBL Bluetooth speaker that I can use with my iPhone for music. It does need to be charged, but doesn't need to be plugged in to 120VAC for use. It has AUX. jack as well as Bluetooth so you can plug in RCA cord between it and a device ( like a TV ).

If your television has an earphone jack you can simply plug in a set of computer speakers. We did that and it gave us stereo sound or individual volume control. With one speaker mounted on each side at the back of the trailer, we can each sit under and control our own volume. Or we can sit across from the television and run it as stereo.